SALT LAKE CITY — Leashes won't be required, but dogs won't be allowed to run as freely at Parleys Historic Nature Park.

By a 4-3 vote Tuesday night, the Salt Lake City Council approved a plan that seeks to balance the 63-acre park's existing use as an off-leash dog area with needs for environmental restoration and improving water quality in Parleys Creek.

The council's decision creates a 50-foot buffer along Parleys Creek that neither people nor dogs can access, while allowing dogs to remain off leashes along designated trails and open, flat areas. No dogs will be allowed on the sloped areas of the park, and they no longer can access the park from the south-side entrance at 2870 East.

The action seeks to address water quality concerns brought to the City Council's attention this week in a letter from Salt Lake County Watershed Planning and Restoration. According to the letter, E. coli counts in July 2010 increased so dramatically that they "exceeded the ability of our methodology to read."

According to the county watershed officials, the likely source of the contamination is pet waste.

City officials say the 50-foot buffer between park users and the creek should allow vegetation to filter possible contaminates before run-off reaches the creek.

The split vote of the council leaves open the possibility that Mayor Ralph Becker will use his power of veto for the first time. Action taken by the council allows much more off-leash dog access in the park than the plan Becker proposed in May.

Becker presented a revised management plan to the City Council on Tuesday — one that increased the amount of off-leash dog area on the east side of the park from his previous plan while prohibiting dogs from the south side of the park.

Becker said the council's decision to allow dogs on the south side of the park "causes me great concern, both from an environmental standpoint and from a user standpoint."

Becker's spokeswoman, Lisa Harrison Smith, has said the mayor would veto a plan that allowed dogs on the south side.

As of Tuesday night, Becker said he was still considering a veto and that he would make a decision on the matter soon.

"I'm not going to take a lot of time thinking about this," he said. "We've all been working on this for a long time."

Councilman Soren Simonsen said he believes the City Council's action respects its July 2007 decision to designate the park near 2700 East and 2700 South as an off-leash dog area. At the same time, it recognizes that action needs to be taken to protect the area's environmental integrity.